This section provides background information related to the present disclosure which is not necessarily prior art.
Thermoelectric materials are known to convert thermal energy directly into electrical energy or vice versa. The efficiency of a thermoelectric material is typically characterized by the thermoelectric figure of merit, (Z) which is defined as the square of its Seebeck coefficient times its electrical conductivity a (sigma) divided by its thermal conductivity κ (kappa) or Z=S2σ/κ (Equation 1). The Seebeck coefficient is a measure of the “thermoelectric pumping power”, which is the amount of heat that a material can pump per unit of electrical current. The electrical conductivity is a measure of electrical losses in a material, and the thermal conductivity is a measure of heat that is lost as it flows back against the heat pumped by a material. The figure of merit Z depends on the macroscopic transport parameters of the materials, thus, a large figure of merit is provided by a thermoelectric material having a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity.
The Seebeck coefficient is further defined as the ratio of the open-circuit voltage to the temperature difference between the hot and cold junctions of a circuit exhibiting the Seebeck effect, or S=V/(TH−TC). Since Z varies with temperature, a useful dimensionless figure-of-merit can be defined as ZT.